The interesting thing is just having the cat motivated James to improve his life. Bob became his friend when the rest of the world ignored him. There are also some unexpected benefits of having Bob around. The story goes through all the difficulty James has trying to overcome both drug addiction and homelessness.
In general, the book is an example of how helping someone can only come back to you in good ways.
Anyway, it’s a short novel and only took me a few hours to read it over the weekend.
Check out the video of James and Bob.